CN110476080A - Laser radar apparatus and method for being scanned to scan angle and for analyzing processing detector - Google Patents

Abstract

A kind of open method for being scanned to scan angle and for analyzing processing detector (4), in the method, in order to be scanned to scan angle, at least one beam (7) is generated by beam source (6), at least one beam (9) reflected on object (12) is received by receiving optical device (16), and it will be on the detector surface (18) of the beam deflection that reflected to the detector (4), seek the duration flight (t) for the beam (9) that at least one is reflected, at least one received beam (11) of institute of analysis processing, wherein, according at least one received beam (11) duration flight, select at least one region (22 of the detector surface (18), 24, 26) at least one received beam (1 of institute is handled to analyze 1).A kind of laser radar apparatus used to perform the method is also disclosed.

Description

LiDAR for scanning the scan angle and for analyzing the detector equipment and methods

technical field

The invention relates to a lidar device and a method for scanning a scanning angle and for evaluating selected detector regions.

Background technique

In the LIDAR (Light detection and ranging: light detection and ranging) device, the distance between the laser radar device and the object is obtained. To this end, light pulses or light beams are generated and emitted along the scan angle. If the object is within the scanning angle, the beam is reflected and can be detected by the detector of the LiDAR system. The time-of-flight of the beam from the instant of generation to the instant of detection can be measured and converted to a distance on the basis of the beam's speed of light. This method is also known as the "Time-of-Flight" method. The detectors in LiDAR devices are usually formed from a linear or planar matrix or array, which consists of a plurality of detector pixels. In a dual-axis LiDAR device, the emitter and receiver are located on separate optical axes. The resulting beam of light can be deflected within the field of view by means of mirrors or rotating components. A spatial angle can thus be scanned. In normal operating conditions of the LiDAR device, the received radiation beams fall on different regions of the detector. Consequently, the detector is not fully illuminated, but essentially partially illuminated. In conventional LIDAR devices, the entire surface of the detector is always evaluated for processing the received radiation, since the irradiated area on the detector and the position of the received radiation are unknown. Alternatively, a region on the detector can be iteratively defined by several measurements for further analysis processing. This results in a large amount of data, which can lead to higher computational complexity or slower evaluation of the detector data.

Contents of the invention

The object underlying the invention can be seen as proposing a method and a laser radar system with a detector which has an improved dynamic range and a reduced The amount of data.

This object is solved by means of the corresponding subjects of the independent claims. Advantageous refinements of the invention are the subject matter of the subclaims in each case.

According to one aspect of the invention, a method is provided for scanning a scan angle and for evaluating a detector. In the method, at least one beam is generated by a beam source for scanning the scan angle. At least one beam reflected on the object is received by the receiver optics, deflected onto the detector surface of the detector, and the flight duration of the at least one reflected beam is ascertained. The at least one received radiation beam is then evaluated, wherein at least one region of the detector surface is selected for evaluation of the at least one received radiation beam as a function of the flight duration of the at least one received radiation beam.

Depending on the distance of the object or target object from the detector, the received radiation beams impinge on different positions on the detector surface of the detector. Depending on the shape of the beam, the received beam impinging on the detector surface forms a measuring point or a measuring surface here. From the geometric relationship between the beam generator, the detector and the object on which at least one generated beam is reflected, it can be determined by means of the flight time of the generated beam from the moment of generation until the moment of detection as follows Location or area: The location or area at which the reflected beam can impinge on the detector surface. This can be achieved in particular by a constant and known distance between the beam generator and the detector, since this changes the angle of incidence of the reflected beam via the receiving optics or directly onto the detector surface. As the angle of incidence of the reflected beam varies, the area irradiated by the reflected beam deviates. This deviation is directly dependent on the object's time-of-flight or distance from the detector. Thus, by ascertaining the time-of-flight of the generated beam, it is possible to predict the area on the detector surface which is irradiated by the reflected beam. As a result, the entire detector surface does not have to be evaluated for further evaluation of the reflected radiation. Conversely, with this method it is possible to select a region on the detector surface which is preferably smaller than the detector surface. Since the entire detector surface is no longer used for evaluating the radiation, the number of measured values can be reduced and the evaluation or processing of the detected radiation can be accelerated. During the parallel evaluation of a plurality of detected reflected radiation beams, the number of detector pixels to be evaluated can be reduced, thereby reducing the circuit complexity. In the case of sequential or continuous analysis processing, the analysis processing can be accelerated.

According to an exemplary embodiment of the method, at least one region of the detector surface is selected as a function of the speed of light, the focal length of the receiving optics and the distance between the beam source and the detector. In practice, the distance from the beam generator to the object is greater than the distance from the beam generator to the detector, which results in a small angle of incidence of the reflected beam. As the distance of the object from the beam source decreases, the area on the detector surface illuminated by the reflected beam is displaced from the initial area. This continuous shift or deviation can be calculated by dividing the product of the focal length of the receiving optics and the distance from the detector to the beam source by the distance from the object to the beam source. Here, the distance between the object and the beam generator can alternatively be expressed as the product of the speed of light and the flight duration of the generated beam.

According to another embodiment, the selected at least one region is moved in at least one dimension along the detector surface depending on the flight duration of the at least one received beam. Thus, after generation of the beam at the beam source, an area on the detector surface can be activated as a function of the flight duration from a defined side (or detector edge) of the detector surface to the opposite side of the detector surface, in order to detect the reflected beam. In this case, the regions on the detector surface are preferably columns on the detector. This reduces the circuit complexity of the detector. The detectors are preferably activated only in selected or calculated regions. Outside the selected area, the detector remains disabled. Preferably, the region activated and ready for detecting the reflected beam is moved along the detector surface in at least one dimension.

According to a further embodiment of the method, the sensitivity of the detector pixels of the detector is selected as a function of the flight duration of at least one received beam. It is advantageous for the detector surface to have a variable sensitivity based on the knowledge that at small distances from the object to the source of the beam, the reflected beam tends to reach a defined side of the detector surface, between the object and the beam source. At greater distances from the beam source, the reflected beam tends to reach the opposite side of the detector. Since the intensity of the reflected radiation is reduced in the remote region, the region of the detector surface which is irradiated by the reflected radiation from a long distance can be made more sensitive. Conversely, the region of the detector surface illuminated by the beam reflected by an object at a close distance to the beam source can be made less sensitive due to the higher intensity of the reflected beam in the short-range region. in order to avoid oversaturation of the detector. In this way, in particular the dynamic range of the detector can be increased, so that the detector always has optimal detection properties not only for distant objects but also for nearby objects.

According to a further embodiment, the area of the region of the detector surface selected for the evaluation of the received radiation is increased or decreased as a function of the interfering reflections. The area of this region can thus be defined or adjusted in such a way that disturbing reflections fall onto forbidden regions of the detector surface. False detections caused by ambient light can thus be prevented.

According to a further aspect of the present invention, a lidar system is provided for carrying out the method for scanning a scanning angle and evaluating a detector according to the preceding aspect of the invention. The lidar device has at least one beam source for generating at least one beam and a unit for emitting the generated beam into a scanning angle. The lidar device also has receiving optics for receiving at least one beam reflected on the object and for deflecting the received beam onto a detector surface of the detector, wherein according to at least one The duration of the flight of the received radiation makes it possible to select the region of the detector surface which is used for the evaluation of at least one received radiation.

With a two-axis LiDAR device, the reflected beam is imaged at different positions on the detector surface of the detector, depending on the distance of the object or target object. When the distance between the target object and the lidar device changes continuously, the position of the measurement point on the detector surface is continuously displaced in one direction. For example, if the beam source is located to the left of the detector beam source, the position of the received beam moves from right to left on the detector surface as the target object moves away from the detector, and when the target object moves away from the detector As the distance to the detector decreases, the position of the received beam moves from left to right on the detector surface. Based on the calculation of the flight duration of the received beam, the position of the received beam at the detector surface can be predicted. By knowing exactly the area on the detector surface of the detector which is irradiated by the received beam, it is no longer necessary to use the entire detector area for evaluating the received beam, but rather a limited area of the detector surface part of the area. As a result, the number of measured values produced by the detector or used for further evaluation can be reduced.

According to an exemplary embodiment of the lidar device, the detector surface has at least two detector pixels distributed over the detector surface. The detector surface of the detector preferably consists of a plurality of detector pixels which are distributed regularly or irregularly over the detector surface. The detector pixels can be, for example, diodes or can be, for example, pixels of a CCD sensor or a CMOS sensor or the like.

According to a further embodiment, the region of the detector surface selected for evaluating the received radiation has at least one detector pixel. This prevents the selection of regions in which the received beams can no longer be physically detected. The measured data of at least one detector pixel can thus be used for further evaluation of the received radiation.

According to a further embodiment of the lidar device, the sensitivity of the detector pixels is implemented to be variable along the detector. In the case of an object at a great distance from the source of the beam, the reflected beam has a lower intensity when received than a beam reflected on a nearby object. Thus, detector pixels may have a variable sensitivity distribution over the detector surface. Regions of the detector surface covering in particular the remote region can have a high sensitivity, and regions of the detector surface detecting the short-range region can be made less sensitive. As a result, distant objects can be detected uniquely and unambiguously, and at the same time overexposure in the case of close objects or reaching the saturation limit of the detector pixels of the detector can be avoided. The dynamic range or working range of the detector can be increased by the variable sensitivity distribution of the detector pixels.

According to a further preferred embodiment, the sensitivity of the detector pixels can be adapted along the detector to the flight duration of at least one received beam. In this case, the light sensitivity or sensitivity of individual detector pixels on the detector surface can be adapted. Since the beam source and the detector are always arranged at the same distance and angle to one another, at least one measurement signal of an object in the remote area or the short-range area is always generated in the same area on the detector surface. This means that the detector area for detecting beams reflected by objects in the remote area can be embodied more light-sensitive than the area for detecting beams reflected by objects in the short-range area. As a result, the saturation limit can be increased or the linear operating range of the detector can be extended. Variable sensitivity can be achieved, for example, by different diode types, by different operating points of the detector pixels or by different fill factors. Here, the fill factor corresponds to the ratio of the photoactive surface to the entire detector surface. For example, the sensitivity of the detector surface can be implemented to be proportional to the square of the distance of the object from the beam source, or to be linear.

According to a further embodiment of the lidar device, the region of the detector is a column of at least one detector pixel. The regions can thus be embodied in the form of columns which occupy the entire height of the detector surface. Depending on the flight duration of the received radiation beams, the region selected for evaluation can thus be displaced along the detector in at least one dimension. As a result, the circuit outlay for matching the selected regions can be reduced, and the selection of relevant relevant measurement data can be technically simplified.

Description of drawings

A preferred embodiment of the invention is explained in more detail below on the basis of highly simplified schematic diagrams.

Shown here:

FIG. 1 shows a schematic diagram of a laser radar device according to a first embodiment of the present invention;

2 shows a schematic diagram of a lidar device according to a second embodiment of the present invention;

Fig. 3 shows a schematic diagram of a lidar device according to a third embodiment of the present invention.

In the figures, identical elements have the same reference numerals, respectively.

Detailed ways

FIG. 1 shows a schematic diagram of a lidar device 1 according to a first embodiment of the invention. The lidar device 1 is used in particular to carry out the method for scanning within the scanning angle 2 and for evaluating the detector 4 . According to this exemplary embodiment, lidar device 1 has a beam source 6 which is an infrared laser 6 . The beam source 6 can generate a pulsed or continuous electromagnetic beam 7 or infrared beam 7 . The beam 7 is emitted into the scan angle 2 via the unit 8 . According to this embodiment, unit 8 is a collimating optic. Additionally, unit 8 may comprise a rotatable mirror (which may alternatively be a stationary mirror), filters, prisms and the like. The unit can optionally change the exit direction of the beam 7 so that the beam 7 preferably illuminates the entire scanning angle 2 .

If object 10 , 12 , 14 is located within scanning angle 2 , generated beam 7 is reflected at object 10 , 12 , 14 . After impinging on object 10 , 12 , 14 , generated beam 7 becomes reflected beam 9 . The reflected radiation beam 9 is then received by the reception optics 16 . Here, for the sake of simplicity, the receiving optics 16 are represented as convex lenses 16 . The receiving optics 16 may be an optical lens system that also has coated lenses, mirrors, filters, diffractive optical elements, and the like. Reflected beam 9 is received by reception optics 16 and deflected as received beam 11 onto detector 4 . In this case, the receiving optics 16 can be rigid or dynamic or, like the unit 8 , movable. Here, the reflected beam 9 is at the angle of incidence The light falls onto the receiving optics 16 . The receiving optics 16 is arranged at a defined distance L from the beam source 6 and has a focal length f. In this case, the detector surface 18 is separated from the receiving optics 16 by the focal length f. For the sake of clarity, the refraction or diffraction of the reflected radiation beam 9 by the receiving optics 16 is not shown in the figure.

According to this embodiment, the detector surface 18 of the detector 4 is shown. The detector surface 18 has a plurality of detector pixels 20 and is used for detecting the received radiation beam 11 . In this case, the detector pixels 20 are, for example, photodiodes. Alternatively, the detector pixels 20 can also be pixels of a CCD sensor or a CMOS sensor. In this case, all detector pixels 20 are formed identically on detector surface 18 and are distributed uniformly over detector surface 18 . Rather, detector pixels 20 form a matrix of rows and columns. Depending on the distance D of the beam source 6 or emission unit 8 to the object 10 , 12 , 14 , the reflected beam 9 has different angles of incidence At this angle of incidence, the reflected beam 9 impinges on the receiving optics 16 or on the detector 4 . Depending on the distance D of the object 10 , 12 , 14 , the received radiation beam 11 impinges on different regions 22 , 24 , 26 of the detector surface 18 . The closer the objects 10 , 12 , 14 are positioned to the beam source 6 , the further the received beam 11 is irradiated from the left side 28 of the detector surface 18 . Therefore, the distance ΔL to the left of the detector 18 can be calculated according to the following formula:

ΔL=f·L/D

In this case, the distance D can be expressed by the flight duration t of the generated beam 7 starting from the beam source 6 or unit 8 until it impinges on the detector 4:

ΔL=2·f·L/(t·c0)

Depending on the type of receiving optics 16, possibly with the angle of incidence Diffraction or refraction of the received radiation beam 11 occurs offset, so that corresponding factors have to be taken into account when calculating the distance ΔL. When the received radiation beam 11 impinges on the detector surface 18 , the received radiation beam 11 is converted by the detector pixel 20 into at least one electrical signal in the form of a voltage. Each detector pixel 20 generates its own electronic signal. After the received radiation beam 11 has impinged on the detector surface 20 , the flight duration t and the distance D of the objects 10 , 12 , 14 can be determined without extensive evaluation. In order to be able to ascertain further information, such as the shape of the beam 11 , the intensity of the beam 11 and the reflectivity of the objects 10 , 12 , 14 , further evaluations are required. Since the time-of-flight has already been ascertained, regions 22 , 24 , 26 on detector surface 20 can be selected for further evaluation. It is therefore not necessary to evaluate the signals of all detector pixels 20 , but only the electronic signals of the detector pixels 20 which directly record the received beam 11 or beams 11 . Advantageously, adjacent detector pixels 20 can also be incorporated into selected areas 22, 24, 26 in order to compensate for tolerances and ensure that no information is lost

FIG. 2 shows a schematic view of a detector 4 according to a second embodiment. Compared to the detector 4 according to the first exemplary embodiment, the detector 4 here has detector pixels 20 which have a different sensitivity. In this case, the sensitivity is high on the left side 28 of the detector surface 18 , since the received radiation beam 11 from an object 14 which is farther away from the device 1 falls here. On the right side 30 of the detector surface 18, the detector pixels 20 are less sensitive or less sensitive, because the reflected received beam from a closer object hits there, and therefore, the received beam 11 The intensity is substantially high and there is a risk of oversaturation of the detector pixels 20 in this region. Here, the sensitivity of the detector pixels 20 is adjusted linearly from a high sensitivity on the left 28 to a low sensitivity on the right 30 . Alternatively, the course of the sensitivity can run quadratically or exponentially.

FIG. 3 shows a schematic illustration of a detector 4 according to a third exemplary embodiment. In contrast to the second exemplary embodiment, here the sensitivity of the detector pixels 20 or the sensitivity of the area on the detector surface 18 is adjusted via the detector pixel density. This means that, on the detector surface 18 , more detector pixels 20 are available for detecting the remote region, while fewer detector pixels 20 are used for the short-range region.

Claims (11)

1. method of the one kind for being scanned to scan angle and for analyzing processing detector (4), wherein

In order to be scanned to the scan angle, at least one beam (7) is generated by beam source (6),

It by receiving optical device (16) receives at least one beam (9) reflected on object (12), and will be reflected In beam deflection to the detector surface (18) of the detector (4),

The duration flight (t) for the beam (9) that at least one is reflected is sought,

At least one received beam (11) of institute of analysis processing,

It is characterized in that, according at least one the duration flight (t) of received beam (11) select the detector table At least one region (22,24,26) in face (18) handles at least one received beam (11) of institute to analyze.

2. according to the method described in claim 1, wherein, according to the light velocity (c0), the focal length (f) for receiving optical device (16) And the distance between the beam source (6) and the reception optical device (16) (L) select the detector surface (18) At least one region (22,24,26).

3. method according to claim 1 or 2, wherein according at least one received beam (11) flight took Time (t) makes at least one selected region (22,24,26) along the detector surface (18) at least one dimension Upper movement.

4. according to the method in any one of claims 1 to 3, wherein according at least one received beam (11) Duration flight (t) selects the sensitivity of the detector pixel (20) of the detector (4).

5. method according to claim 1 to 4, wherein increase or reduce the detection according to noisy reflection The area in the region (22,24,26) on device surface (18).

6. a kind of laser radar apparatus (1), the laser radar apparatus is for executing according to any one of the preceding claims institute The method for being scanned to scan angle and for analyzing processing detector (4) stated, the laser radar apparatus have For generating at least one beam source (6) of at least one beam (7), for generated beam (7) to be emitted to scan angle Interior unit (8) and receive optical device (16), the receptions optical device be used to receive at least one object (10,12, 14) beam (9) that is reflected on and for by received beam (11) deflect into the detector surfaces (18) of detector (4) On, to analyze processing, at least one passes through the received beam (11) of reception optical device (16) institute, which is characterized in that root According at least one the duration flight (t) of received beam (11) the following area of the detector surface (18) can be selected Domain (22,24,26): the region is for analyzing at least one received beam (11) of institute of processing.

7. laser radar apparatus according to claim 1, wherein the detector surface (18), which has, is distributed in the spy Survey at least two detector pixels (20) on device surface (18).

8. laser radar apparatus according to claim 1 or 2, wherein the region of the detector surface (18) (22,24,26) there is at least one detector pixel (20).

9. laser radar apparatus according to any one of claim 1 to 3, wherein the spirit of the detector pixel (20) Sensitivity, which is implemented as, to be changed along the detector surface (18).

10. laser radar apparatus according to any one of claim 1 to 4, wherein the spirit of the detector pixel (20) Sensitivity can be matched with along the detector (4) at least one received beam (11) duration flight (t).

11. laser radar apparatus according to any one of claim 1 to 5, wherein the area of the detector (4) Domain (22,24,26) is the column being made of at least one detector pixel (20).